In a portable working machine represented by an engine cutter, a wheel guard is provided so that scattering of cut powder to the surrounding area is prevented during a grinding operation. For working machines to which a wheel guard is provided, it is required to prevent a situation in which the wheel guard is rotated and displaced when a part (piece) of the wheel guard that is damaged during the grinding operation collides with the wheel guard.
Therefore, to prevent the wheel guard from rotating more than necessary, attaching a stopper for preventing rotation like Japanese Patent Application Laid-Open Publication No. 10-86136 has become common. Furthermore, increasing the thickness of the wheel guard or manufacturing with a material having high strength have been widely implemented.